This grant continues the biochemical studies to clarify the possible role of osteoblasts and osteoclast collagenase in bone resorption. Basic knowledge for the understanding of destructive processes of bone and periodontal tissue will be of vital importance in controlling and preventing alveolar bone loss in periodontal disease, which accounts for more than half of the total tooth mortality in the United States. Based on the accumulated evidence suggesting that osteoblasts and collagenase synthesized by osteoblasts may play an important role in osteoclastic bone resorption, we plan to develop the following two basic areas of research with five specific aims for the next three years of our study. I. Collagenase Synthesis and Regulation in Osteoblasts 1. Pulse-chase analysis of biosynthetic process of collagenase in mouse osteoblastic clonal MC3T3-E1 cells. 2. In vitro translation of collagenase messenger RNA isolated from MC3T3-E1 cells and analysis of primary collagenase synthetic products. II. Cell-Mediated Resorption of Living Bone 1. Study of the possible temporal sequence for synthesis and secretion of collagenase and lysosomal enzymes in both medium and bone samples during bone resportion in tissue culture. 2. Unilateral inhibition of collagenase or lysosomal enzymes with appropriate inhibitors to analyze the possible temporal relationship between these enzymes during bone resorption. 3. Isolation and characterization of factor(s) synthesized by mouse osteoblastic clonal MC3T3-E1 cell, which stimulate bone resorption in tissue culture.